This work investigates alterations in activity or concentration of various brain enzymes and substrates in response to exposure to anoxia or hypoxia. Changes in water and electrolyte content also are examined in cortex, basal ganglia, and hemispheral white matter. Tissues are assayed both during and following exposure to episodes of anoxia and hypoxia. Comparisons are made of changes in enzyme activities and substrate concentrations in brains of animals that develop brain edema and those that recover without brain injury.